Driver assistance systems are increasingly used in motor vehicles, in particular cars, trucks or motorcycles. Conventional driver assistance systems also help to automatically adjust vehicle headlamps with different light distributions. The adjustment of the light distribution is thereby usually based on a recognized current driving situation of the motor vehicle in question. Traffic indicators in the vehicle's surroundings can be taken into account as well.
DE 10 2013 213 375 A1, which is incorporated by reference describes a method for controlling the light distribution produced by one headlamp on a motor vehicle. In this case, a camera system onboard the motor vehicle images a scene ahead of the motor vehicle and this scene is subsequently evaluated. Finally, the light distribution produced by the at least one headlamp of the motor vehicle is controlled as a function of the result of the image evaluation. In the course of the image evaluation, traffic indicators are detected in the method described in DE 10 2013 213 375 A1 and compared with stored patterns. In the case of a recognized correspondence between a detected traffic indicator and a specific stored pattern, a light distribution which is assigned to the stored pattern is automatically adjusted from a multiplicity of possible different light distributions. FIG. 1 shows a table listing road signs and the associated light distributions which are switched on, off or over when the respective road sign is recognized, which is used in this conventional method.
However, the disadvantage of the method for controlling the light distribution described in DE 10 2013 213 375 A1 is that it does not operate reliably and/or it can easily be disrupted. This is explained below with reference to the traffic situations illustrated in FIGS. 2A, 2B and 3A, 3B.
As can be seen in FIG. 2A, a vehicle F is moving on a roadway and/or road and passes a first road sign VS1 which shows a 10 percent downhill gradient of the road, at a time t1. In the conventional method, in accordance with the table shown in FIG. 1, the headlamps of the vehicle F are consequently lowered in order, on the one hand, to better illuminate the road ahead of the vehicle and, on the other hand, to dazzle other road users, which are approaching the vehicle on the other side of the road, less. If, for example, in the traffic situation illustrated in FIG. 2A, the vehicle F passes the second road sign VS2 which indicates a speed limit of 60 km/h, after a few meters, at a time t2, the headlamps of the vehicle F are raised again in accordance with the table illustrated in FIG. 1. The consequence of this is that if the road continues to descend, the road ahead of the vehicle is only poorly illuminated due to the raised vehicle headlamps and, at the same time, drivers of oncoming vehicles are dazzled.
In the traffic situation illustrated in FIG. 2B, the vehicle F first passes a road sign VS3 which displays a speed limit and then a road sign VS4 which indicates a downhill gradient of the road of 10%. In both of the traffic situations illustrated in FIGS. 2A, 2B, the order of the road signs is therefore reversed. In the traffic situation illustrated in FIG. 2B, the vehicle headlamps are first raised and then lowered in accordance with the table illustrated in FIG. 1. In the traffic situation illustrated in FIG. 2B, due to the order in which the vehicle passes the two road signs VS3, VS4 which happens to coincide with said vehicle descending the downhill gradient, the road ahead of the vehicle is illuminated in an advantageous manner due to the lowered vehicle headlamp, at the same time preventing oncoming road users from being dazzled. As is clear from FIGS. 2A, 2B, the illumination of the roadway in the conventional method is therefore dependent on the order of the road signs located at the edge of the road. This is also made clear by means of the example illustrated in FIGS. 3A, 3B. In the example illustrated in FIG. 3A, the vehicle F first passes a road sign VS5 which indicates the possibility of wild animals crossing. In accordance with the table indicated in FIG. 1 dipped headlights and a turn light are activated, in order to better illuminate the lateral edge of the road. The vehicle F then passes a road sign VS6 which indicates a speed limit of 60 km/h at a time t2. In accordance with the default according to the table in FIG. 1, the headlamps of the vehicle F are consequently automatically raised. If, for example, the road sign VS6 is located just a few meters behind the road sign VS5, the vehicle does not drive through the danger area in which wild animals may cross in accordance with the default indicated for the road sign VS5, but in accordance with the default for the speed limit traffic indicator VS6. FIG. 3B shows the reverse order where a road sign VS7 first indicates a speed limit and then a road sign VS8 displays the hazard of wild animals crossing. When the two road signs VS7, VS8 are in this order, the headlamps of the vehicle F are first raised at a time t1 and then the dipped headlights and the turn light are switched on at a time t2 in order to illuminate the lateral areas of the road in accordance with the table in FIG. 1. As can be seen by comparing FIGS. 3A and 3B, the vehicle headlamps are controlled here as well depending on the random order of the two road signs.
In the conventional control method, as described in DE 10 2013 213 375 A1, there is therefore a risk that, on the one hand, the road ahead of the vehicle is not optimally illuminated and, on the other hand, drivers of oncoming vehicles may be significantly dazzled.